This invention relates to a gentle abrasive toothpaste containing calcined kaolin and a hydrating silica gel. More particularly, this invention relates to a toothpaste containing calcined kaolin as the sole abrasive therein, and having low abrasivity while maintaining desirable rheological properties.
The function of abrasives in toothpaste formulations for use in the oral cavity is to remove various deposits, including pellicle film, from the surface of the teeth. Pellicle film is tightly adherent and is partly responsible for the yellow or brownish discoloration of the teeth. A toothpaste therefore should be abrasive enough to maximize removal of this film and other undesired deposits without causing undue abrasion to the surface of the tooth. Dental research is continually concerned with developing toothpaste compositions that demonstrate satisfactory levels of cleaning and that are not unduly abrasive and damaging to the teeth.
U.S. Pat. No. 4,122,163 discloses a toothpaste using calcined kaolin as an abrasive. The kaolin is said to be predominantly of the gamma alumina or mullite form.
U.S. Pat. No. 4,414,199 discloses a toothpaste using calcined kaolin as an abrasive. The kaolin is at least 80% calcined to the mullite crystal form and has a particle size distribution such that more than 50% of the particles are between 1 to 10 microns and less than 5% exceed 10 microns. These toothpastes have a Radioactive Dentin Abrasion of about 124 as determined by the Radioactive Dentin Abrasion Index.
Merely reducing the level of kaolin in the toothpaste formulation results in lower abrasivity, but results in the need for increased levels of conventional thickeners such as gums or other solids such as alumina, calcium carbonate, calcium pyrophosphate, and dicalcium phosphate. An increased level of thickeners in the toothpaste formulation, however, imparts a greater degree of stringiness to the toothpaste and results in poor toothpaste break off properties (the ability of the toothpaste to cleanly come away from the tube when applied to a toothbrush).
Adding other solids such as calcium carbonate, calcium pyrophosphate, and dicalcium phosphate may provide a desirable rheology and break off properties, but they may reduce the availability of soluble fluoride ion because they react with fluoride. Moreover, these solids have inherently high abrasives qualities, which makes their use undesirable. Accordingly, it is a primary object of this invention to produce toothpaste compositions having reduced abrasivity, without sacrificing desirable rheological properties or fluoride availability.